In spite of the progress made in the understanding of the biology, genetics and immunology of melanoma, the outcome for patients with advanced-stage disease has remained poor. A step forward toward better therapies was recently provided by the improvement in overall survival observed in melanoma patients treated with an anti-CTLA4 antibody. Attempts to further augment the efficacy of this treatment would still face however a variety of immunosuppressive factors operative in melanoma-bearing hosts. Among those, one that has gained much attention is the ability of melanoma tumors to induce T-cell tolerance. Our studies to date of the epigenetic regulation of T-cell unresponsiveness point to histone deacetylase inhibitors (HDI) as promising immunomodulatory compounds given their dual ability to influence the immunogenicity of melanoma tumors and enhance T-cell function. These observations together with our additional findings that HDAC6 and HDAC11 regulates melanoma immunogenicity and T-cell responsiveness respectively, provided the rationale to mechanistically address the role of HDACs in melanoma immunobiology. The hypothesis to be tested is therefore whether epigenetic manipulation of specific HDACs might augment the immunogenicity of melanoma cells and/or augment T-cell responses leading to breaking of immune tolerance and enhancement of the efficacy of CTLA4 blockade. The animal models, molecular and pharmacological tools we have in hands together with the access (through the Pathology Core of this SPORE) to human melanoma samples would allow us to gain insights into the role of HDAC6 in melanoma proliferation, survival and immunogenicity (Aim 1), and the role of HDAC11 in T-cell anti-melanoma immunity (Aim 2). In addition, the expertise provided by the Clinical Core will allow the successful completion of a Phase I clinical trial aimed to assess the safety and immunologic effects of HDAC inhibition in combination with an anti-CTLA4 antibody in patients with stage IV melanoma (Aim 3). The new knowledge to be generated by this team effort would lead to novel epigenetic-based immunotherapy that by overcoming the remarkable barrier of melanoma-induced T-cell tolerance would improve the efficacy of CTLA4 blockade.